The present invention relates to a body fluid treating apparatus used in a body fluid treating circuit wherein the blood or other body fluid is withdrawn from the human body, subjected to an appropriate treatment with a treating device and returned to the human body, and a method for treating body fluid. More particularly, the present invention relates to the treating apparatus and method comprising the use of a plurality of treating devices which are sequentially and alternately put into a treatment mode in such a manner that while one of the devices is on the treatment mode, the other devices are on a regeneration mode, with the switching of any of the devices from one mode to the other being effected safely and surely.
The term "body fluid" as used herein means any fluid matters, including blood, lymph and ascites, that exist in the human body.
The term "body fluid treatment" as used herein means application of a treatment to body fluids, e.g. removal of harmful or unnecessary components, addition of medicinally effective substances, supplementation of deficient components, substitution of one component with another.
A method of treating a body fluid in which the body fluid is withdrawn from a human body, extracorporeally treated and returned to the body, namely a so-called extracorporeal circulation treatment, has heretofore been applied to treatment of various diseases. For example, this treatment is effective for hyperlipidemia, drug intoxication, fulminant hepatitis, macroglobulinemia, multiple myelitis, serious akinesia, rheumatoid arthritis, hepatic failure, lupus erythematosus, nephritis and other diseases.
FIG. 5 is a schematic view showing a conventional body fluid treating circuit used for selective removal of low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL), which are chief etiologic factors in hyperlipidemia, from blood of a patient with hyperlipidemia. This body fluid treating circuit is composed of blood collection block 20, blood treatment block 40, and blood return block 60.
In the blood collection block 20, there are disposed collected blood pressure gage 21, blood pressure abnormality detector 22, blood collection pump 23, anticoagulant pump 24 for heparinization, drip chamber 25, plasma separation pressure gage 26 and so on, so that the blood collection may be performed continuously and safely. In addition, supply source 27 for a circuit washing liquid (e.g. physiological saline or Ringer's solution) and liquid discontinuation sensor 28 are connected in position near the blood collection end.
The treatment block 40 where blood is subjected to a predetermined treatment, includes plasma separator 41, plasma pressure gage 42, blood leak detector 43, plasma pump 44, supply side drip chamber 45, supply blood pressure gage 46, treating device 47 for removal of LDL and VLDL from the plasma, filter 48 for preventing incorporation of adsorbent, etc., return side drip chamber 49, and delivery blood pressure gage 50, and so on.
In the body fluid return block 60, there are disposed heating bag 61, drip chamber 62, return blood pressure gage 63, and air bubble detector 64 so that the treated blood may be safely returned to human body 70.
The treatment with the above body fluid treating circuit is explained below.
First, from the patient's body 70, the blood is withdrawn by the blood pump 23, while a proper blood collection pressure is maintained. While the anti-coagulant heparin is infused from the anti-coagulant pump 24 into the blood, the collected blood is guided to the plasma separator 41. In this plasma separator 41, a portion or all of the plasma fraction of the blood is separated and sent to the treating device 47, while the remainder of the blood flows along. The treating device 47 is packed with an adsorbent which adsorbs to remove LDL and VLDL in the separated plasma while it flows through the device. The treated plasma is joined together with the blood cell fraction which has passed through the plasma separator 41, and the mixed blood is warmed to a suitable temperature in the heating bag 61 before being returned to the human body.
However, in clinical use, the above body fluid treating circuit has the following disadvantages.
(i) During blood treatment, the entire circuit is full of the blood. This means that a substantial quantity of blood is taken outside the patient's body. Since this condition may cause anemia, there is a certain limitation in the scaling-up of the treating device.
(ii) Since the amount of extracorporeal circulation of the blood is large, the treatment can hardly be applied to underweight, anemic, or hypotensive patients.
(iii) As a preparatory procedure for body fluid treatment, circuit elements are assembled and the circuit is washed with physiological saline or the like by passing through it. Therefore, before start of the treatment, the circuit is in the state of being full of the washing liquid. As the treatment proceeds, the washing liquid enters into the patient's body, thus it tends to reduce the colloid osmotic pressure of the blood which may cause a blood pressure drop.
In order to solve the above disadvantages, the present applicant proposed a body fluid treating circuit in which a plurality of treating devices with a reduced capacity than conventional one are provided, as disclosed in Japanese Patent Publication Kokai No. 164562/1986. FIG. 6 shows the treatment zone in the proposed circuit. A plurality of small treating devices 51, 52 are installed in parallel within the treatment zone and these small devices 51, 52 are equipped with a body fluid sending out system including washing liquid supply source 53 and delivery pump 54, and a washing liquid discharge line 55. In this arrangement, by operating these small devices 51, 52 in turn, the extracorporeal circulation volume of the blood can be decreased. Moreover, by withdrawing the pre-filled washing liquid from the small treating devices 51, 52 through the discharge line 55 before starting the treatment, the drop in colloid osmotic pressure can be prevented. The above body fluid treating circuit can overcome the above-mentioned disadvantages (i) to (iii).
However, the above proposed body fluid treating circuit is still inadequate and has the following disadvantage.
(iv) Although the extracorporeal circulation volume of blood and the volume of inflow of the washing liquid into the human body are both decreased, the total amount of adsorbent required per treatment remains unchanged. Therefore, if one tries to reduce the capacity of each small treating device, an increased number of small treating devices has to be provided. Moreover, since such small treating devices are discarded after use, it is inevitable to incur an increased equipment cost and, hence, an increased cost of medical treatment.
In Japanese Patent Publication Kokai No. 162953/1986, the present applicant disclosed a technique for regenerating the adsorption ability of the used adsorbent, wherein after LDL and VLDL are adsorbed by an adsorbent composed of a water-insoluble support such as cellulose and a polyanion compound, such as dextran sulfate, immobilized onto the support, the adsorbent is washed with a highly concentrated aqueous solution of an electrolyte (0.18 to 6 moles/liter) to elute the LDL and VLDL.
When this regeneration method is applied to the above proposed body fluid treating circuit, one may alternately and repeatedly operate a plurality of small treating devices provided in the treatment zone by regenerating the used treating device while the body fluid is treated by the other device. This means that the number of small treating devices can be held to the necessary minimum and, therefore, the above-mentioned disadvantage (iv) can be eliminated.
However, when this regeneration technique is applied to the above-mentioned body fluid treating circuit using a plurality of small treating devices, the following new problem is encountered. That is, the aqueous electrolyte solution (regenerating liquid) for regeneration of the adsorbent contains electrolytes in concentrations higher than the physiological saline and, if it comes into contact with body fluids, the salt concentrations of the body fluids are inevitably increased. Moreover, if the regenerating liquid remains in the device, it would inflow into the patient's body to cause various disturbances.